EP0363435B1 - Verfahren zur herstellung von supraleitern - Google Patents

Verfahren zur herstellung von supraleitern Download PDF

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EP0363435B1
EP0363435B1 EP88906392A EP88906392A EP0363435B1 EP 0363435 B1 EP0363435 B1 EP 0363435B1 EP 88906392 A EP88906392 A EP 88906392A EP 88906392 A EP88906392 A EP 88906392A EP 0363435 B1 EP0363435 B1 EP 0363435B1
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suspension
temperature
cupric
aqueous solution
carboxylate
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EP0363435A1 (de
EP0363435A4 (de
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Harold Saul Horowitz
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EIDP Inc
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EI Du Pont de Nemours and Co
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G3/00—Compounds of copper
    • C01G3/006—Compounds containing, besides copper, two or more other elements, with the exception of oxygen or hydrogen
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/45—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides
    • C04B35/4504—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides containing rare earth oxides
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/45—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides
    • C04B35/4512—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides containing thallium oxide
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/45—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides
    • C04B35/4521—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides containing bismuth oxide
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/01—Manufacture or treatment
    • H10N60/0268—Manufacture or treatment of devices comprising copper oxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/76—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by a space-group or by other symmetry indications
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/725—Process of making or treating high tc, above 30 k, superconducting shaped material, article, or device
    • Y10S505/734—From organometallic precursors, e.g. acetylacetonates
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/725—Process of making or treating high tc, above 30 k, superconducting shaped material, article, or device
    • Y10S505/737—From inorganic salt precursors, e.g. nitrates
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/725—Process of making or treating high tc, above 30 k, superconducting shaped material, article, or device
    • Y10S505/737—From inorganic salt precursors, e.g. nitrates
    • Y10S505/738—From inorganic salt precursors, e.g. nitrates by precipitating

Definitions

  • This invention relates to an improved process for making copper oxide-containing superconductors.
  • the superconducting phase has been identified as the composition La 1-x (Ba,Sr,Ca) x CuO 4-y with the tetragonal K2NiF4-type structure and with x typically about 0.15 and y indicating oxygen vacancies.
  • the reacted mixture was pulverized and the heating step was repeated.
  • the thoroughly reacted mixture was then pressed into 3/16 inch (0.5 cm) diameter cylinders for final sintering at 925°C for 24 hours in the same reduced oxygen atmosphere.
  • the material prepared showed the existence of multiple phases.
  • the powders were heated for 8-10 hours at 1000°C, ground and then cold pressed to form disks of about 1 cm diameter and 0.2 cm thickness.
  • the superconducting properties of samples prepared in these two ways were similar. X-ray diffraction examination of the samples revealed the existence of multiple phases.
  • Takita et al. Jpn. J. Appl. Phys. 26 , L506-L507 (1987), disclose the preparation of several Y-Ba-Cu compositions with superconducting transitions around 90 K by a solid-state reaction method in which a mixture of Y2O3, CuO, and BaCO3 was heated in an oxygen atmosphere at 950°C for more than 3 hours. The reacted mixture was pressed into 10 mm diameter disks for final sintering at 950° or 1000°C for about 3 hours in the same oxygen atmosphere.
  • Takayama-Muromachi et al. Jpn. J. Appl. Phys. 26 , L476-L478 (1987), disclose the preparation of a series of samples to try to identify the superconducting phase in the Y-Ba-Cu-O system.
  • Appropriate amounts of Y2O3, BaCO3 and CuO were mixed in an agate mortar and then fired at 1173 ⁇ 2 K for 48-72 hours with intermediate grindings.
  • X-ray diffraction powder patterns were obtained.
  • the suggested composition of the superconducting compound is Y 1-x Ba x CuO y where 0.6 ⁇ x ⁇ 0.7.
  • Oxalic acid was used as the precipitant and insoluble Ba, Y and Cu compounds were formed at a constant pH of 6.8.
  • the decomposition of the precipitate and the solid-state reaction were performed by firing in air at 900°C for 2 hours.
  • the fired products were pulverized, cold-pressed into pellets and then sintered in air at 900°C for 5 hours.
  • the diffraction pattern was obtained and indexed as having tetragonal symmetry.
  • Hikami et al., Jpn. J. Appl. Phys. 26 , L347-L348 (1987), disclose the preparation of a Ho-Ba-Cu oxide, exhibiting the onset of superconductivity at 93 K and the resistance vanishing below 76 K, by heating a mixture of powders Ho2O3, BaCO3 and CuO with the composition Ho:Ba:Cu 0.246:0.336:1 at 850°C in air for two hours. The sample was then pressed into a rectangular shape and sintered at 800°C for one hour. The sample looked black, but a small part was green.
  • the samples show an onset of superconductivity at 85 K and a vanishing resistance at 45 K.
  • the material made from ultrapure oxides has a superconducting transition with a midpoint of 22 K as determined from resistivity measurements and zero resistance below 14 K.
  • the material made from commercial grade oxides has a superconducting transition with a midpoint of 7 K.
  • a mixture of Bi2O3, CuO and SrCO3 was heated at 800°C for 12 hours in air, sintered at 900°C for 2 hours in air and quenched to room temperature.
  • the superconducting metal oxide phase having the formula Bi2Sr 3-z Ca z Cu2O 8+w wherein z is from about 0.1 to about 0.9, preferably 0.4 to 0.8 and w is greater than zero but less than about 1.
  • the pellet was then put into a tube furnace which had been heated to 880-910°C and was heated for 2-5 minutes in flowing oxygen. As soon as it had slightly melted, the sample was taken from the furnace and quenched in air to room temperature. It was noted by visual inspection that Tl2O3 had partially volatilized as black smoke, part had become a light yellow liquid, and part had reacted with Ba-Cu oxide forming a black, partially melted, porous material.
  • Tl-Ba-Ca-Cu-O system Tl2Ba2Ca2Cu3O10 and Tl2Ba2CaCu2O8 and the method of preparation.
  • Appropriate amounts of Tl2O3, CaO, and BaCu3O4 or Ba2Cu3O4 were completely mixed, ground and pressed into a pellet.
  • a quartz boat containing the pellet was placed in a tube furnace which had been preheated to 880-910°C. The sample was heated for 3 to 5 minutes in flowing oxygen and the furnace cooled to room temperature in 1 to 1.5 hours.
  • Subramanian et al., Nature 332, 420 (1988) disclose the preparation of superconducting phases in the Tl-Ba-Ca-Cu-O system by reacting Tl2O3, CaO2 or CaCO3, BaO2 and CuO at 850-910°C in air or in sealed gold tubes for 15 minutes to 3 hours.
  • the present invention provides an improved process for preparing a precursor to a copper oxide-containing superconducting composition.
  • the composition may be of a rare earth metal- , bismuth- or thallium-based alkaline earth metal-copper-oxide composition.
  • the process for preparing the superconducting composition involves heating the precursor and in addition, in the case of the rare earth metal-based compositions, cooling the previously-heated precursor under prescribed conditions.
  • the resulting superconducting powder can be pressed into a desired shape and then, under prescribed conditions, sintered, and for the rare earth metal-based compositions cooled, to provide a superconducting shaped article.
  • This invention also includes providing the shaped articles prepared by the process of the invention.
  • the invention involves preparing the precursor from an aqueous suspension by mixing an aqueous solution of a carboxylate e.g. an acetate or a nitrate of copper at a temperature of 50-100°C with either (1) a hydroxide or an oxide or a peroxide of an alkaline earth metal, e.g. barium, calcium or strontium and bismuth oxide (Bi2O3) or thallium oxide (Tl2O3) or a rare earth oxide, e.g. Y2O3, or (2) a hydroxide of the alkaline earth metal and a carboxylate or a nitrate of bismuth, thallium or the rare earth.
  • a carboxylate e.g. an acetate or a nitrate of copper
  • a temperature of 50-100°C with either (1) a hydroxide or an oxide or a peroxide of an alkaline earth metal, e.g. barium, calcium or strontium and bismuth oxide
  • the relative quantities of the compounds are selected to provide the atomic ratios of M (Bi, Tl or rare earth) -to- A (alkaline earth metal) -to-copper -to- oxygen that are known to provide superconducting compositions e.g. M(rare earth)Ba2Cu3O x where x is 6.5-7.0, Bi2Sr2CuO x where x is 6-6.5, Bi2Sr2CaCu2O x where x is 8-9, Tl2Ba2CuO x where x is 6-6.5, Tl2Ba2CaCu2O x where x is 8-9, Tl2Ba2Ca2Cu3O x where x is 10-11.5.
  • the invention as it relates to the rare earth metal-containing superconducting compositions involves a process for preparing a superconducting composition having the formula MBa2Cu3O x wherein M is selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu; x is from about 6.5 to about 7.0; said composition having a superconducting transition temperature of about 90 K; said process consisting essentially of
  • the invention provides an improved process for preparing a superconducting composition of bismuth-based alkaline earth metal-copper-oxide wherein the alkaline earth metal is Sr or both Sr and Ca; the process consisting essentially of
  • Bi:Sr:Ca:Cu are in the atomic ratios 2:2:0:1 or 2:2:1:2 and the respective superconducting oxide has the nominal formula Bi2Sr2CuO where x is from about 6 to about 6.5 or the nominal formula Bi2Sr2CaCu2O x , where x is from about 8 to about 9, both with orthorhombic symmetry.
  • the invention also provides an improved process for preparing a superconducting composition of thallium-based alkaline earth metal-copper-oxide wherein the alkaline earth metal is Ba or both Ba and Ca; the process consisting essentially of
  • Tl:Ba:Ca:Cu are in the atomic ratios 2:2:0:1, 2:2:1:2 or 2:2:2:3 and the respective superconducting oxide has the nominal formula Tl2Ba2CuO x where x is from about 6 to about 6.5, the nominal formula Tl2Ba2CaCu2O x where x is from about 8 to about 9 or the nominal formula Tl2Ba2Ca2Cu3O x where x is from about 10 to about 11.5, all with tetragonal symmetry.
  • the various products of the process of this invention is a nearly single-phase superconducting oxide. No additional grinding, annealing or refining is necessary to produce the superconducting oxide composition.
  • a suspension is prepared which is then used to generate a precursor powder for later heating.
  • the suspension is prepared by using, as the source of the alkaline earth metal, the alkaline earth metal hydroxide, the alkaline earth metal peroxide or the alkaline earth metal oxide.
  • the alkaline earth metal hydroxide is used.
  • the alkaline earth metal hydroxide can be added as an aqueous solution. If the alkaline earth metal peroxide is used, it should be added slowly to the solution of the copper compound because of the evolution of oxygen.
  • the copper compound used in preparing the suspension is an aqueous, preferably concentrated, solution of cupric carboxylate or cupric nitrate.
  • the source of copper is cupric carboxylate. Suitable carboxylates include the formate, acetate, and other water soluble carboxylates, but the acetate is preferred.
  • the suspension is prepared by mixing either M2O3 as a source of the rare earth metal, Bi2O3 as a source of bismuth, or Tl2O3 as a source of thallium and the alkaline earth metal compound with an aqueous solution of cupric carboxylate or cupric nitrate at a temperature from about 50°C to about 100°C.
  • the rare earth metal, bismuth or thallium compound and the alkaline earth metal compound are mixed together prior to addition to the aqueous solution.
  • the suspension is prepared by mixing the alkaline earth metal compound with an aqueous solution of copper carboxylate, nitrate or a mixture thereof and either a rare earth metal or a thallium carboxylate, nitrate or a mixture thereof at a temperature from about 50°C to about 100°C.
  • the preferred source of copper is a cupric carboxylate and of these the acetate is preferred.
  • the source of the rare earth metal is a rare earth metal carboxylate.
  • Suitable carboxylates include the acetate and other water soluble carboxylates, but the acetate is preferred. This latter embodiment of the invention can also be used to prepare the bismuth-based oxide.
  • the low solubilities of the bismuth salts such as bismuth nitrate, bismuth acetate and the other bismuth carboxylates offer no significant advantage regarding homogeneity of the suspension formed over that obtained by using Bi2O3 as in the previous embodiment.
  • the concentration of the aqueous solution is below saturation, and heating can be effected before, during or after the solids are added.
  • the resulting suspension is then dried to remove the solvent and form the powder precursor. Drying can be effected by conventional techniques. For instance, drying can be accomplished by continued heating of the suspension at a temperature from about 50°C to about 100°C while the suspension is stirred. As the solvent is removed from the suspension, the viscosity of the suspension increases until a thick paste is formed. This paste is further heated at a temperature from about 100°C to about 200°C to produce the precursor solid which is then gently milled to form a powder precursor. Alternatively, the suspension can be spray-dried or freeze-dried using conventional techniques to produce a powder precursor without milling.
  • the powder precursor can be heated in an oxygen-containing atmosphere at a temperature appropriate for the specific metal-based oxide, where for the rare earth metal-based oxide the temperature is from about 850°C to about 950°C, for the bismuth-based oxide the temperature is from about 850°C to about 875°C, and for the thallium-based oxide the temperature is from about 850°C to about 920°C, for a time sufficient to form the superconducting oxide except in the case of the rare earth metal-based oxide where the product formed is during the heating is maintained in an oxygen-containing atmosphere while cooling for a time sufficient to form the superconducting oxide.
  • the powder precursor is placed in a non-reactive container, e.g., an alumina or gold crucible or tray.
  • the superconducting product powder can be pressed into a desired shape and then sintered in an oxygen-containing atmosphere at a temperature as indicated above for the preparation of the specific metal-based oxide, i. e., for the rare earth metal-based oxide the temperature is from about 850°C to about 950°C, for the bismuth-based oxide the temperature is from about 850°C to about 875°C, and for the thallium-based oxide the temperature is from about 850°C to about 920°C, with the proviso that in the case of the rare earth metal-based oxide the shaped article is maintained in an oxygen-containing atmosphere while cooling.
  • a temperature as indicated above for the preparation of the specific metal-based oxide i. e., for the rare earth metal-based oxide the temperature is from about 850°C to about 950°C, for the bismuth-based oxide the temperature is from about 850°C to about 875°C, and for the thallium-based oxide the temperature is from about 850°C to about 920°
  • the process of this invention provides a method for preparing a superconducting composition that requires no special atmosphere during the heating step, no subsequent grinding, reheating or annealing, no extended heating times and no refining of the product to separate the desired superconducting composition from other phases.
  • the product of the process of the invention involving the use of the rare earth metal is essentially a single-phase, superconducting compound with orthorhombic symmetry. No additional grinding, annealing or refiring is necessary to produce the MBa2Cu3O x composition.
  • the process of the invention is an improved process for preparing superconducting compositions having the formula MBa2Cu3O x , M being selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, preferably Y.
  • the parameter x is from about 6.5 to about 7.0, but is preferably from about 6.8 to 7.0.
  • a suspension is prepared which is then used to generate a precursor powder for later heating.
  • the suspension is prepared by using, as the source of barium, Ba(OH)2 ⁇ 8H2O, BaO2 or BaO.
  • Ba(OH)2 ⁇ 8H2O is used. If BaO2 is used, it should be added slowly to the Cu solution because of the evolution of oxygen.
  • the second component used in preparing the suspension is an aqueous, preferably concentrated, solution of cupric carboxylate or cupric nitrate.
  • the source of copper is cupric carboxylate. Suitable carboxylates include the formate, acetate, and other water soluble cupric carboxylates, but the acetate is preferred.
  • the suspension is prepared by mixing M2O3 and the barium compound with an aqueous solution of cupric carboxylate or cupric nitrate at a temperature from about 50°C to about 100°C.
  • the M2O3 and barium compound are mixed together prior to addition to the aqueous solution.
  • the suspension is prepared by mixing the barium compound with an aqueous solution of Cu carboxylate, nitrate or a mixture thereof and M carboxylate, nitrate or a mixture thereof at a temperature from about 50°C to about 100°C.
  • the preferred Cu source is the same as for the other embodiment.
  • the rare earth metal source is an M carboxylate.
  • Suitable carboxylates include the acetate, and other water-soluble carboxylates, but the acetate is preferred.
  • the concentration of the aqueous solution is below saturation, and heating of the aqueous solution can be effected before, during or after the solids are added.
  • the relative amounts of the sources of M, Ba and Cu used in forming the suspension from which the precursor is prepared are chosen such that the atomic ratio of M:Ba:Cu is about 1:2:3.
  • the starting materials used in the process of the invention are of relatively high purity, e.g., 99.9% by weight for copper acetate, 99.99% by weight for copper nitrate, >98% by weight for Ba(OH)2 ⁇ 8H2O, 99.5% by weight for BaO2 and 99.9% by weight for M2O3.
  • Less pure starting materials can be used; however, the product may then contain an amount of another phase material comparable to the amount of impurity in the starting materials. It is particularly important to avoid the presence of impurities containing iron and other transition, but non-rare earth, metals in the reactants.
  • the resulting suspension is then dried to remove the solvent and form the powder precursor. Drying can be effected by conventional techniques.
  • drying can be accomplished by continued heating of the suspension at a temperature from about 50°C to about 100°C while the suspension is stirred. As the solvent is removed from the suspension, the viscosity of the suspension increases until a thick paste is formed. This thick paste is further heated at a temperature from about 100°C to 200°C to produce the precursor solid which is then gently milled to form a powder precursor.
  • the suspension can be spray dried or freeze-dried using conventional techniques to produce a powder precursor without milling.
  • the powder precursor is then heated in an oxygen-containing atmosphere at a temperature from about 850°C to about 950°C, preferably from about 875°C to about 900°C, for a time sufficient to form MBa2Cu3O y , where y is from about 6.0 to about 6.4. It has been determined by TGA that when the powder precursor is heated to 900°C, y is from about 6.0 to about 6.4.
  • the powder precursor is placed in a non-reactive container, e.g., an alumina or gold crucible or tray.
  • the oxygen-containing atmosphere can be air or oxygen gas, but is preferably air.
  • the container with the powder precursor is placed in a furnace and brought to a temperature of about 850°C to about 950°C.
  • the total time that the powder precursor is at temperatures in this range that is important. For example, when a heating rate of 20°C per minute is used to raise the temperature of the furnace containing the sample from ambient temperature to a final heating temperature is 900°C, 1/2 to 2 hours at this temperature are sufficient to produce, after cooling as prescribed herein, practically single-phase superconducting MBa2Cu3O x . Longer heating times can be used. At the end of the heating time, the furnace is turned off, and the resulting material is allowed to cool in the oxygen-containing atmosphere for a time sufficient to obtain the desired product. Preferably, the material is cooled to below about 100°C (a time interval of about 4-5 hours) before the sample container is removed from the furnace.
  • the oxygen content of the material increases to give the desired MBa2Cu3O x product.
  • the additional oxygen which enters into the crystalline lattice of the material during this cooling step to form the desired product does so by diffusion.
  • the rate at which oxygen enters the lattice is determined by a complex function of time, temperature, oxygen content of the atmosphere, sample form, etc. Consequently, there are numerous combinations of these conditions that will result in the desired product. For example, the rate of oxygen uptake by the material at 500°C in air is rapid, and the desired product can be obtained in less than an hour under these conditions when the sample is in the form of a loosely packed, fine particle powder.
  • the MBa2Cu3O x powder can be pressed into a desired shape, sintered in an oxygen-containing atmosphere at a temperature from about 900°C to about 950°C, and maintained in the oxygen-containing atmosphere while cooling as prescribed above to obtain a MBa2Cu3O x shaped article.
  • Well sintered, shaped articles will take longer to form the desired product while cooling than will more porous ones, and for larger, well sintered, shaped articles many hours may be required.
  • a convenient procedure for obtaining the desired product when the material is in the form of a powder or a small shaped object is to turn off the furnace in which the heating was conducted and to allow the material to cool in the furnace to a temperature approaching ambient (about 22°C) which typically requires a few hours.
  • ambient about 22°C
  • cooling in the furnace to below about 100°C was found to be sufficient.
  • Increasing the partial pressure of oxygen in the atmosphere surrounding the sample during cooling increases the rate at which oxygen enters the lattice.
  • the material is cooled in such a manner that the MBa2Cu3O x product is not obtained, the material can be heated to an intermediate temperature, such as 500°C, between ambient temperature and the final temperature used in the heating step and held at this temperature for a sufficient time to obtain the desired product.
  • an intermediate temperature such as 500°C
  • the product formed is practically single-phase and has orthorhombic symmetry as determined by X-ray diffraction measurements.
  • the process of this invention as it relates to the rare earth metal superconductor provides a method for preparing a superconducting MBa2Cu3O x composition that does not require a special atmosphere during the heating step, subsequent grinding, reheating or annealing, extended heating times or refining of the product to separate the desired superconducting MBa2Cu3O x composition from other phases.
  • the phrase "consisting essentially of” means that additional steps can be added to the process of the invention so long as such steps do not materially alter the basic and novel characteristics of the invention.
  • the presence of superconductivity at any given temperature can be determined by the Meissner effect, i. e., the exclusion of magnetic flux by a sample when in the superconducting state.
  • the invention is further illustrated by the following examples in which temperatures are in degrees Celsius unless otherwise indicated.
  • the chemicals (with purity indicated) used in the following examples of the process of this invention were Ba(OH)2 ⁇ 8H2O - (>98%) obtained from Morton Thiokol Inc. or Research Organic/Inorganic Chemical Corp., BaO2 - (99.5%) obtained from Atomergic Chemetals Corp., Cu(C2H3O2)2 ⁇ H2O - (99.9%) obtained from J. T.
  • This paste was further heated until dry to obtain a solid which was placed in a vacuum oven at 170° for 1 hour. The solid was then converted to a dark brown powder by hand grinding in an agate mortar and pestle.
  • the X-ray diffraction pattern of this precursor solid showed that it was predominantly amorphous with some very poorly crystalline CuO also evident in the x-ray diffraction pattern.
  • the yield was 25.90 g.
  • a 5.26 g portion of the above precursor was spread into a thin layer in an alumina tray and heated in air in a furnace from ambient temperature to a final heating temperature of 900° at a rate of about 20° per minute. The temperature was maintained at 900° for 2 hours. The furnace was then turned off and allowed to cool to a temperature below 100° before the sample was removed. The resulting product was black and the yield was 3.14 g.
  • An X-ray diffraction powder pattern of the product showed that it was YBa2Cu3O x .
  • the indices of the observed reflections, the d-spacings and relative intensities are shown in Table I.
  • a 1.08 g portion of the precursor powder prepared using a procedure very similar to that described in Example 1 was spread into a thin layer in an alumina tray and heated in air in a furnace from ambient temperature to a final heating temperature of 900° at a rate of about 20° per minute. The temperature was maintained at 900° for 30 minutes. The furnace was turned off and allowed to cool below 100° before the sample was removed. The product was black and the yield was 0.66 g. An X-ray diffraction powder pattern of the material showed that the product was orthorhombic YBa2Cu3O x . The results were very similar to those given in Table I. There were also slight traces of BaCuO2, Y2Cu2O5 and BaCO3.
  • This paste was further heated until dry and the resulting solid was placed in a vacuum oven at 170° for 1 hour.
  • the solid was then converted to a dark brown powder by hand grinding in an agate mortar using a pestle.
  • the X-ray diffraction powder pattern of this precursor solid showed that the powder was amorphous with some poorly crystalline CuO and a small amount of a poorly crystalline unidentified phase also present.
  • the yield was 46.51 g.
  • a 21.2 g portion of this precursor powder was spread into a thin layer in an alumina tray and heated in air in a furnace from ambient temperature to a final heating temperature of 900° at a rate of about 20° per minute. The temperature was maintained at 900° for 8 hours. The furnace was then turned off and allowed to cool to a temperature below 100°C before the sample was removed. The product was black and the yield was 14.25 g.
  • An X-ray diffraction powder pattern of the material showed that it was orthorhombic YBa2Cu3O x , and the results were very similar to those given in Table I. Trace amounts of BaCuO2 and Y2Cu2O5 are also evident in the pattern.
  • a 1.14 g of precursor powder made by a procedure very similar to that described in Example 3 was spread into a thin layer in an alumina tray and heated in air in a furnace from ambient temperature to a final heating temperature of 900° at a rate of about 20° per minute. The temperature was maintained at 900° for 2 hours. The furnace was then turned off and allowed to cool to a temperature below 100°C before the sample was removed. The product was black. An X-ray diffraction powder pattern of the material showed that it was orthorhombic YBa2Cu3O x , and the results were very similar to those given in Table I. Trace amounts of BaCuO2 and Y2Cu2O5 are also evident in the pattern.
  • the suspension was kept stirred and heated at about 75° for a little less than one hour.
  • the heated suspension was then sprayed through an air atomization nozzle into a covered beaker containing liquid nitrogen.
  • the nozzle manufactured by Spraying Systems Co., Wheaton, Illinois, was Model 9265-1/4 J-LUC fitted with fluid cap # 2850-LUC, liquid orifice diameter of 0.7 mm (0.028 in) and air cap # 70-LUC.
  • the nozzle was pressurized by 140 kPa (20 psi) of air.
  • the resulting slurry of liquid nitrogen and finely divided frozen powder was then freeze dried.
  • the powder obtained was medium grey and very fluffy.
  • a 1.05 g portion of this freeze-dried powder was spread in a thin layer in an alumina tray and heated in air in a furnace from ambient temperature to a final heating temperature of 900° at a rate of about 20° per minute. The temperature was maintained at 900° for 2 hours. The furnace was turned off and allowed to cool below 100° before the sample was removed. The resulting powder was black and the yield is 0.61 g.
  • An X-ray diffraction powder pattern of the material showed that the product was orthorhombic YBa2Cu3O x , and the results were very similar to those given in Table I. There were a minor impurity of Y2Cu2O5 and a trace amount of Y2BaCuO5. Measurement of the Meissner effect showed the powder to have a T c onset of about 90 K.
  • the heated suspension was then spray dried using a Buchi laboratory Model spray dryer operated with an inlet temperature of 215°.
  • the resulting powder was a medium grey, free-flowing powder made up of spherical agglomerates, characteristic of the spray-drying process.
  • the yield was 13.03 g.
  • a portion (1.25 g) of this precursor powder was spread into a thin layer in an alumina tray and then heated in air in a furnace from ambient temperature to a final heating temperature of 875° at a rate of about 20° per minute. The temperature was maintained at 875° for 2 hours. The furnace was turned off and allowed to cool below 100° before the sample was removed. The resulting product was black and the yield was 0.72 g.
  • An X-ray diffraction powder pattern of the material showed that the product was orthorhombic YBa2Cu3O x , and the results were very similar to those given in Table I. There were trace amounts of BaCuO2 and Y2Cu2O5.
  • Cu(NO3)2 ⁇ 6H2O (10.65 g, 0.036 mole) was dissolved in 25 cc of distilled water.
  • Y(NO3)3 ⁇ 6H2O (5.39 g, 0.012 mole) was dissolved in 25 cc of H2O.
  • These two solutions were added together to yield a mixed solution of copper and yttrium nitrates which was then heated to about 75°.
  • Ba(OH)2 ⁇ 8H2O (7.57 g, 0.024 mole) was then slowly added with stirring to the heated solution. A light blue suspension was obtained. This suspension was kept stirred and heated at about 75° until a paste was obtained. This paste was further heated until dry and the resulting solid was placed in a vacuum oven at 170° for several hours.
  • the solid was then converted to a light blue powder by grinding by hand using an agate mortar and pestle.
  • An X-ray diffraction powder pattern of this precursor showed that it to consisted of a crystalline unidentified phase or phases.
  • the yield was 14.69 g.
  • a portion (1.12) g of this precursor powder was spread into a thin layer in an alumina tray and heated in air in a furnace from ambient temperature to a final heating temperature of 875° at a rate of about 20° per minute. The temperature was maintained at 875° for 2 hours. The furnace was turned off and allowed to cool substantially as described in previous examples. The resulting powder was black and the yield was 0.62 g.
  • An X-ray diffraction powder pattern of the material showed that the product was orthorhombic YBa2Cu3O x , and the results were very similar to those given in Table I. There were minor amounts of BaCuO2 and CuO also present. Measurement of the Meissner effect showed the powder to have a T c onset of about 90 K.
  • This paste was further heated until dry to obtain a solid which was placed in a muffle furnace in air at 150° for about 16 hours. The solid was then converted to a dark brown powder by grinding it by hand using an agate mortar and pestle. The yield was 11.24 g.
  • a portion (1.11 g) of this precursor powder was spread into a thin layer in an alumina tray and heated in air in a furnace from ambient temperature to a final heating temperature of 875° at a rate of about 20° per minute. The temperature was maintained at 875° for 2 hours. The furnace was then turned off and allowed to cool substantially as described in the previous examples to give 0.76 g of a black product.
  • An X-ray diffraction powder pattern of the product showed that it was orthorhombic YBa2Cu3O x , and the results were very similar to those given in Table I. There were trace amounts of BaCuO2, Y2Cu2O5 and BaCO3.
  • a portion (1.11 g) of this precursor powder was heated in air in a furnace from ambient temperature to a final heating temperature of 875°C at a rate of about 20°C per minute. The temperature was maintained at 875°C for 2 hours. The furnace was then turned off and allowed to cool to a temperature below 100°C before the sample was removed. The product was black and the yield was 0.79 g.
  • An X-ray diffraction powder pattern of the product showed that it was the orthorhombic phase with the nominal formula Bi2Sr2CaCu2O8+y plus a small amount of orthorhombic Bi2Sr2CuO 6+x . Measurement of the Meissner effect showed the powder to have a T c onset of about 72 K.
  • the solid is then converted to a powder by grinding it by using an agate mortar and pestle.
  • This precursor powder can then be heated in air in a furnace to a final heating temperature of about 850°C to about 915°C and maintained at that temperature for 15 minutes to 2 hours.
  • the product will be the tetragonal phase with the nominal formula Tl2Ba2CaCu2O8+y.

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Claims (15)

  1. Verfahren zur Herstellung einer supraleitenden Zusammensetzung der Formel



            M₁Ba₂Cu₃Ox



    worin
    M   aus Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb und Lu ausgewählt ist und
    x   ein Zahlenwert im Bereich von etwa 6,5 bis 7,0 ist,
    umfassend
    (a) das Bilden einer Suspension durch Vermischen von Bariumhydroxid und M₂O₃ mit einer wäßrigen Lösung eines Kupfer(II)-carboxylats oder von Kupfer(II)-nitrat bei einer Temperatur von etwa 50 °C bis etwa 100°C oder Vermischen von Bariumhydroxid mit einer wäßrigen Lösung eines Kupfer(II)-carboxylats oder von Kupfer(II)-nitrat und eines M-carboxylats oder von M-nitrat bei einer Temperatur von etwa 50 °C bis etwa 100°C, um eine Suspension zu erhalten, in der M : Ba : Cu in einem Atom-Verhältnis von etwa 1 : 2 : 3 vorhanden sind;
    (b) Trocknen der in Schritt (a) gebildeten Suspension zur Gewinnung einer Vorstufe; und
    (c) Erhitzen der Vorstufe in einer Sauerstoff enthaltenden Atmosphäre auf eine Temperatur von etwa 850 °C bis etwa 950 °C während eines Zeitraums, der zur Bildung von



            M₁Ba₂Cu₃Oy



    ausreicht, worin
    y   etwa 6,0 bis 6,4 ist, und
    Halten des M₁Ba₂Cu₃Oy in einer Sauerstoff enthaltenden Atmosphäre während eines Zeitraums, der zur Gewinnung von M₁Ba₂Cu₃Ox ausreicht.
  2. Verfahren nach Anspruch 1, worin die Suspension durch Vermischen von Bariumhydroxid und M₂O₃ mit einer wäßrigen Lösung von Kupfer(II)-acetat gebildet wird.
  3. Verfahren nach Anspruch 1, worin die Suspension durch Vermischen von Bariumhydroxid mit einer wäßrigen Lösung von Kupfer(II)-acetat und M-acetat gebildet wird.
  4. Verfahren zur Herstellung einer supraleitenden Zusammensetzung der Formel



            Bi₂Sr₂CuOx,



    worin
    x   ein Zahlenwert im Bereich von etwa 6 bis etwa 6,5 ist,
    umfassend
    (a) das Bilden einer Suspension entweder
    (i) durch Vermischen von Strontiumhydroxid, -oxid oder - peroxid und Bi₂O₃ mit einer wäßrigen Lösung eines Kupfer(II)-carboxylats oder von Kupfer(II)-nitrat bei einer Temperatur von etwa 50 °C bis etwa 100°C oder
    (ii) durch Vermischen von Strontiumhydroxid mit einer wäßrigen Lösung eines Kupfer(II)-carboxylats oder von Kupfer(II)-nitrat und eines Bismutcarboxylats oder von Bismutnitrat bei einer Temperatur von etwa 50 °C bis etwa 100°C,
    um eine Suspension zu erhalten, in der
    Bi : Sr : Cu in einem Atom-Verhältnis von etwa
    2 : 2 : 1 vorhanden sind;
    (b) Trocknen der in Schritt (a) gebildeten Suspension zur Gewinnung einer Vorstufe; und
    (c) Erhitzen der Vorstufe in einer Sauerstoff enthaltenden Atmosphäre auf eine Temperatur von etwa 850 °C bis etwa 875 °C während eines Zeitraums, der zur Bildung von Bi₂Sr₂CuOx ausreicht.
  5. Verfahren nach Anspruch 4, worin die Suspension durch Vermischen von Strontiumhydroxid und Bi₂O₃ mit einer wäßrigen Lösung von Kupfer(II)-acetat gebildet wird.
  6. Verfahren nach Anspruch 4, worin die Suspension durch Vermischen von Strontiumhydroxid mit einer wäßrigen Lösung von Kupfer(II)-acetat und Bi-acetat gebildet wird.
  7. Verfahren zur Herstellung einer supraleitenden Zusammensetzung der Formel



            Bi₂Sr₂CaCu₂Ox,



    worin
    x   ein Zahlenwert im Bereich von etwa 8 bis etwa 9 ist,
    umfassend
    (a) das Bilden einer Suspension entweder
    (i) durch Vermischen von Strontiumhydroxid, -oxid oder - peroxid, Calciumhydroxid, -oxid oder -peroxid und Bi₂O₃ mit einer wäßrigen Lösung eines Kupfer(II)-carboxylats oder von Kupfer(II)-nitrat bei einer Temperatur von etwa 50 °C bis etwa 100°C oder
    (ii) durch Vermischen von Strontiumhydroxid und Calciumhydroxid mit einer wäßrigen Lösung eines Kupfer(II)-carboxylats oder von Kupfer(II)-nitrat und eines Bismutcarboxylats oder von Bismutnitrat bei einer Temperatur von etwa 50 °C bis etwa 100°C,
    um eine Suspension zu erhalten, in der
    Bi : Sr : Ca : Cu in einem Atom-Verhältnis von etwa
    2 : 2 : 1 : 2 vorhanden sind;
    (b) Trocknen der in Schritt (a) gebildeten Suspension zur Gewinnung einer Vorstufe; und
    (c) Erhitzen der Vorstufe in einer Sauerstoff enthaltenden Atmosphäre auf eine Temperatur von etwa 850 °C bis etwa 875 °C während eines Zeitraums, der zur Bildung von Bi₂Sr₂CaCu₂Ox ausreicht.
  8. Verfahren nach Anspruch 7, worin die Suspension durch Vermischen von Strontiumhydroxid, Calciumhydroxid und Bi₂O₃ mit einer wäßrigen Lösung von Kupfer(II)-acetat gebildet wird.
  9. Verfahren nach Anspruch 7, worin die Suspension durch Vermischen von Strontiumhydroxid und Calciumhydroxid mit einer wäßrigen Lösung von Kupfer(II)-acetat und Bi-acetat gebildet wird.
  10. Verfahren zur Herstellung einer supraleitenden Zusammensetzung der Formel



            Tl₂Ba₂CuOx,



    worin
    x   ein Zahlenwert im Bereich von etwa 6 bis etwa 6,5 ist,
    umfassend
    (a) das Bilden einer Suspension entweder
    (i) durch Vermischen von Bariumhydroxid, -oxid oder -peroxid und Tl₂O₃ mit einer wäßrigen Lösung eines Kupfer(II)-carboxylats oder von Kupfer(II)-nitrat bei einer Temperatur von etwa 50 °C bis etwa 100°C oder
    (ii) durch Vermischen von Bariumhydroxid mit einer wäßrigen Lösung eines Kupfer(II)-carboxylats oder von Kupfer(II)-nitrat und eines Thalliumcarboxylats oder von Thalliumnitrat bei einer Temperatur von etwa 50 °C bis etwa 100°C,
    um eine Suspension zu erhalten, in der
    Tl : Ba : Cu in einem Atom-Verhältnis von etwa
    2 : 2 : 1 vorhanden sind;
    (b) Trocknen der in Schritt (a) gebildeten Suspension zur Gewinnung einer Vorstufe; und
    (c) Erhitzen der Vorstufe in einer Sauerstoff enthaltenden Atmosphäre auf eine Temperatur von etwa 850 °C bis etwa 920 °C während eines Zeitraums, der zur Bildung von Tl₂Ba₂CuOx ausreicht.
  11. Verfahren nach Anspruch 10, worin die Suspension durch Vermischen von Bariumhydroxid und Tl₂O₃ mit einer wäßrigen Lösung von Kupfer(II)-acetat gebildet wird.
  12. Verfahren nach Anspruch 10, worin die Suspension durch Vermischen von Bariumhydroxid mit einer wäßrigen Lösung von Kupfer(II)-acetat und Tl-acetat gebildet wird.
  13. Verfahren zur Herstellung einer supraleitenden Zusammensetzung der Formel



            Tl₂Ba₂CaCu₂Ox,



    worin
    x   ein Zahlenwert im Bereich von etwa 8 bis etwa 9 ist,
    oder



            Tl₂Ba₂Ca₂Cu₃Ox,



    worin
    x   ein Zahlenwert im Bereich von etwa 10 bis etwa 11,5 ist,
    umfassend
    (a) das Bilden einer Suspension entweder
    (i) durch Vermischen von Bariumhydroxid, -oxid oder -peroxid, Calciumhydroxid, -oxid oder -peroxid und Tl₂O₃ mit einer wäßrigen Lösung eines Kupfer(II)-carboxylats oder von Kupfer(II)-nitrat bei einer Temperatur von etwa 50 °C bis etwa 100°C oder
    (ii) durch Vermischen von Bariumhydroxid und Calciumhydroxid mit einer wäßrigen Lösung eines Kupfer(II)-carboxylats oder von Kupfer(II)-nitrat und eines Thalliumcarboxylats oder von Thalliumnitrat bei einer Temperatur von etwa 50 °C bis etwa 100°C,
    um eine Suspension zu erhalten, in der
    Tl : Ba : Ca : Cu in einem Atom-Verhältnis von etwa
    2 : 2 : 1 : 2 oder 2 : 2 : 2 : 3 vorhanden sind;
    (b) Trocknen der in Schritt (a) gebildeten Suspension zur Gewinnung einer Vorstufe; und
    (c) Erhitzen der Vorstufe in einer Sauerstoff enthaltenden Atmosphäre auf eine Temperatur von etwa 850 °C bis etwa 920 °C während eines Zeitraums, der zur Bildung von Tl₂Ba₂CaCu₂Ox oder Tl₂Ba₂Ca₂Cu₃Ox ausreicht.
  14. Verfahren nach Anspruch 13, worin die Suspension durch Vermischen von Bariumhydroxid, Calciumhydroxid und Tl₂O₃ mit einer wäßrigen Lösung von Kupfer(II)-acetat gebildet wird.
  15. Verfahren nach Anspruch 13, worin die Suspension durch Vermischen von Bariumhydroxid und Calciumhydroxid mit einer wäßrigen Lösung von Kupfer(II)-acetat und Tl-acetat gebildet wird.
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ATE95008T1 (de) 1993-10-15
EP0363435A1 (de) 1990-04-18
CN1031296A (zh) 1989-02-22
CA1337373C (en) 1995-10-24
DK620689A (da) 1990-01-31
JPH02503787A (ja) 1990-11-08
HUT52643A (en) 1990-07-28
KR890702261A (ko) 1989-12-23
DE3884395T2 (de) 1994-04-21
DK620689D0 (da) 1989-12-08
AU2085288A (en) 1989-01-04
US5061683A (en) 1991-10-29
EP0363435A4 (de) 1990-03-22
DE3884395D1 (de) 1993-10-28
AU608640B2 (en) 1991-04-11
CN1028390C (zh) 1995-05-10
NO890562L (no) 1989-04-10
NO180765B (no) 1997-03-03

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